From: Guoniu Zhou Date: Mon, 23 Mar 2026 08:33:31 +0000 (+0800) Subject: media: nxp: imx8-isi: Fix scale factor calculation for hardware rounding X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=5eb54da3f874b44149556542d949909898865e29;p=thirdparty%2Fkernel%2Flinux.git media: nxp: imx8-isi: Fix scale factor calculation for hardware rounding The ISI hardware rounds the actual output size up to an integer, as described in i.MX93 Reference Manual section 57.7.8 (Channel 0 Scale Factor). The scale factor must be calculated to ensure the theoretical output value rounds up to exactly the desired size. Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver") Cc: stable@vger.kernel.org Signed-off-by: Guoniu Zhou Reviewed-by: Laurent Pinchart Link: https://patch.msgid.link/20260323-isi-v3-2-8df53b24e622@oss.nxp.com Signed-off-by: Laurent Pinchart Signed-off-by: Hans Verkuil --- diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c index 0187d4ab97e8..16b20ea2d1db 100644 --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c @@ -112,7 +112,14 @@ static u32 mxc_isi_channel_scaling_ratio(unsigned int from, unsigned int to, else *dec = 8; - return min_t(u32, from * 0x1000 / (to * *dec), ISI_DOWNSCALE_THRESHOLD); + /* + * The ISI rounds output dimensions up to the next integer (i.MX93 RM + * section 57.7.8). Calculate the scale factor such that the theoretical + * output (input / scale_factor) rounds up to exactly the desired + * output. + */ + return min_t(u32, DIV_ROUND_UP(from * 0x1000, to * *dec), + ISI_DOWNSCALE_THRESHOLD); } static void mxc_isi_channel_set_scaling(struct mxc_isi_pipe *pipe,